and then after you've been paying for a subscription for 3 years and you decide you are happy with version X for the time being, you won't be able to continue using it if you stop paying. From the Subscription FAQ:

If I cancel my subscription, does that mean I can still use my software, and that I just won’t receive updates for the most current version?

No. When you cancel your subscription you will no longer have access to any version of your Creative Suite subscription software.